Deodorisation plant for fatty oils

ABSTRACT

A deodorisation plant for treatment of fatty oils comprises a vessel (1) connected to a vacuum source. In the vessel there is a distillation column filled with structured packing material through which column the oil which shall be deodorised is brought to flow under influence of gravity and to meet a deodorisation gas in counter-current. In the vessel there is also a number of trays for collection of oil provided with drainage outlets in their lower part. The oil is treated with deodorisation gas in a batchwise way in these trays. The vessel is provided with an inlet (7) for oil and a connection (2) to a vacuum source in its upper part. In its lower part there is an outlet (9) for oil.

FIELD OF THE INVENTION

The present invention relates to a deodorisation plant for fatty oilscomprising a vessel connected to a vacuum source.

BACKGROUND OF THE INVENTION

When producing consumer products from different vegetable or animal oilsdeodorisation is a part in the refining process. During thedeodorisation the oil is heated to a high temperature 180-275° C. inorder to drive off volatile impurities and undesired substances from theoil. These substances have a lower boiling point than the differenttriglycerides which constitute the fatty oil. The deodorisation iscarried through under vacuum conditions, 1-20 mbar absolute pressure,and the removal is facilitated by addition of deodorisation gas to theoil. The gas facilitates the removal of undesired substances.

On the market there are today a large number of different deodorisationplants, both for continuous flow through the plant and with a batchwisetreatment of the oil. During continuous deodorisation the oil usuallyflows over a number of trays or containers which are stacked verticallyin a circular shell manner. In the bottom of the trays or containersthere are means for addition of gas. Alternatively the gas may be addedby using a means with siphon effect. Oil and gas are forced upwards inan ejector tube towards a deflection plate and is finely divided againstthe same. The oil is added to the vessel in the upper part of the plantand flows from an upper container to the next container. In order tocontrol the flow through the containers these are provided withscreening plates, such that the oil flows from an inlet at a certainplace in the container to an outlet in another place. The holding timein the vessel is set to a certain value depending on the geometry of theflow channels. The switch-over time between different products is long.

When the deodorisation is carried through in batches all operations(distillation and heat holding for bleaching) usually take place in thesame vessel. This method of working makes rapid changes betweendifferent oil products possible, but the holding time is long since itdepends both on distillation and heat transfer effect.

SUMMARY OF THE INVENTION

The present invention offers a solution of the problem to rapidly changethe holding time for different operations in the deodorisation plant butstill make it possible to rapidly change between different oil products.A deodorisation plant according to the invention comprises a vesselconnected to vacuum in which there is both a distillation column filledwith the structured packing material, through which column the oil whichshall be deodorised is brought to flow under influence of the gravityand meet deodorisation gas in counter-current, and a number of trays forcollection of oil provided with drainage outlets in their lower parts,in which trays the oil is treated in batches with deodorisation gas. Thevessel is in its upper part provided with an inlet for oil and aconnection to a vacuum source and with an outlet for oil in its lowerpart.

The column is as mentioned filled with a structured packing material thepurpose of which is to create an increased area of contact and anincreased time for contact between the oil and the deodorisation gas.Such packing material is available on the market and is used for manydifferent purposes. The time for passing the column is usually 5-15 min.Due to the efficiency of the column the desired deodorisation (removalof volatile impurities) may take place also at lower temperatures, whichdiminishes the formation of transfatty acids. The working pressure(vacuum) may be kept low, below 5 mbar and if desired also below 1 mbar.The efficient contact in the column also results in a lower demand onthe amount of deodorisation gas.

Usually the column is arranged uppermost in the vessel, but if it isdesirable one or several trays for a first bachwise treatment may ofcourse be arranged above the column. If the distillation column isarranged at the top of the vessel the oil is suitably added to the sameheated to a desired high temperature. The holding time in the vessel maybe chosen to 20-75 min.

With advantage the trays are without flow directing insets, but providedwith means for supply of deodorisation gas in the vicinity of the bottomof the tray.

A connection for deodorisation gas is arranged in the lower part of thevessel close to the outlet from the vessel.

A deodorisation plant according to the invention is preferably providedwith tubes which connect the space above each tray with the space underthe column, which makes it possible to achieve a desired vacuum level inthe whole vessel.

According to the invention a heat exchanger may with advantage bearranged in the outlet from the vacuum vessel This heat exchanger isdivided in sections which are connected to each other by cut-off valves.In each section there are means for supply of deodorisation gas. Thesections are preferably arranged at different height making it possiblefor the oil to flow from section to section by gravity. The treated oilfrom the vacuum vessel enters the uppermost section. In each sectionthere is also a tube through which oil to be treated in the vessel isdirected. This untreated oil is heated by the treated oil which isvaluable for energy saving reasons. The deodorisation gas, which is usedin the heat exchanger, is led to the space below the column and is usedfor deodorisation purposes also in the column.

BRIEF DESCRIPTION OF DRAWINGS

The deodorisation plant according to the invention is described furtherwith reference to the attached drawing,

FIG. 1 of which shows the plant as such, while

FIG. 2 schematically shows how the plant can be used in order to be ableto change rapidly between different oil products.

FIG. 3 shows a perspective drawing of the heat exchanger connected tothe vacuum vessel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As may be seen in FIG. 1 the deodorisation plant comprises a vessel 1provided with a connection to a vacuum source. In the upper part of thevessel there is a distillation column 3 consisting of a structuredpacking material which completely fills the cross-section of the vessel.In the lower part of the vessel there are bottoms 4, 4' which areprovided with outlet openings 5,5' in their lower part. Below the outletthere are cut-off valves 6, 6'. These bottoms 4, 4' and the circularwalls of the vessel form trays in which the oil is collected. In theupper part of the vessel there is a supply tube 7 for the oil productwhich is to be treated in the vessel. Over the column there are means 8to distribute the added oil product over the whole cross-section of thevessel. In the bottom of the vessel there is also a tray formed by thelower part of the vessel with an outlet 9 through which treated productis drawn away. Outside the vacuum vessel there is a tube 10 whichconnects the space under the lowest bottom 4' with the space under thecolumn 3. Also the space between the bottoms 4 and 4' is connected tothe space under the column 3 through the tubes 10 and 11. Just over thebottoms 4, 4' there are inlet tubes 12, 12' for deodorisation gas. Aninlet tube 13 for such gas is also arranged in the bottom tray.

A plant of the kind shown now may be used in the following way. The oilwhich is to be treated in the deodorisation plant is pretreated in amanner known per se by preheating deaeration and heating with a furtherremoval of air to a deodorisation temperature of 250-260° C.

After this heating the oil is directed into the deodorisation plant byway of the pipe 7 and is distributed over the cross-section of thecolumn 3. The oil flows downwards through the column in the form of thinfilms which continuously are transformed and redivided by the inertpacking material. In the column the oil film meets deodorisation gas incounter-current. In the vessel which by way of the connection 2 isconnected to a vacuum source there is a pressure of 0.5-20 mbar. Thedeodorisation gas usually consists of steam but nitrogen gas or carbondioxid may also be used.

Volatile, undesired products are set free from the oil during influenceof the deodorisation gas and vacuum.

When the oil has passed the column it is collected in a first traysurrounded by the walls of the vessel, which is formed over the bottom4. Close to the bottom 4 there is a means 12 for supply of deodorisationgas. Into this tray the main part of the gas is supplied which gas afterhaving passed the amount of collected oil flows upwards against thelower part of the column. The oil which has flown through the column ina continuous way is collected in the tray which is limited by the bottom4. In this the oil is kept during a desired time, while it is flownthrough by deodorisation gas. During this treatment a chemical effect onthe oil takes place as a consequence of the high temperature. Due to thefact that gas the whole time flows through the oil undesired, breakingdown products are removed.

After the desired holding time the valve 6 is opened and the oil istransferred to the next tray formed by the bottom 4' and the walls ofthe vessel. Also in this tray deodorisation gas is supplied by way ofthe means 12'.

When the desired holding time has been obtained the valve 6' is openedand the oil is collected in the bottom of the vessel. After a suitabletime it is led away through the outlet 9. Deodorisation gas is addedalso here by means 13.

From the vessel 1 the treated oil is directed to a heat exchanger 14where deodorisation gas is added by means 15. In the heat exchangerthere is also an U-tube 16 through which oil, which later is to betreated in the vessel, is forced to flow. The untreated oil is heated bythe deodorised oil leaving the vessel 1. The chilled treated oil leavesthe heat exchanger through the outlet 17. The gas leaves the heatexchanger through the tube 18 which is connected to tube 10. By such anarrangement the gas, which is used for deodorisation in the heatexchanger, is utilized also in the column 3.

In the shown embodiment the plant comprises one column and two trays forbatchwise treatment. Within the limit of the invention it is of coursepossible to work with further columns and fewer or more trays.

As has been described above the trays for the batchwise treatment arecreated by the bottoms and the walls of the vessels. There are no flowdirecting insets in the trays but the oil is only collected until adesired volume has been obtained. The height of the liquid in each traymay be up to 50-60 cm.

FIG. 3 shows the heat exchanger (economiser) 14 in detail. As may beseen in the drawing the heat exchanger is divided into three sections14, 14' 14" which are connected. The oil enters the uppermost section 14through a pipe connected to outlet 9. Deodorisation gas is added to eachsection by means (not shown in the drawing). The gas leaves the sectionsthrough tubes connected to tube 18. The oil to be heated is directed toan U-tube 16 the in- and outlets of which are shown close to the bottomof each section. At the top of the section there are sight glasses.

As mentioned the treated oil enters the uppermost section and leaves thesame after a desired holding time. Between the sections there arecut-off valves 19, 19' which make it possible to use all sections in theheat exchanger in succession or to leave one section empty if onedesires to change between oils of different kinds. The oil flows fromsection to section due to gravity and leaves the heat exchanger throughthe outlet 17.

The deodorisation plant according to the invention presents greatadvantages when one wants to change from one oil product to another. InFIG. 2 it is described schematically how such a change may take place.The valves V1 and V2 close the outlets from the trays, while the valveV3 closes the outlet from the vessel 1.

When the most of the oil in the bottom of the vessel has been emptiedthe oil change is initiated. The supply of oil to the column is stoppedand the oil which is in the column is drained to the upper tray. The oilwhich has been heat treated in the lower tray is transferred to thelower part of the vessel by opening the valve V2. The oil in the uppertray is thereafter directed to the lower tray by opening the valve V1.When the upper tray is emptied and the content in the lower tray hasbeen transferred to the bottom of the vessel 1, oil change may takeplace and new oil is added to the column. The new oil is then collectedin the upper tray while the lower tray is empty.

What is claimed is:
 1. A deodorization plant for treatment of fatty oilscomprising a vessel connected to a vacuum source, said vessel (1)further comprisinga distillation column (3), means for flowing oil to betreated under the influence of gravity through said column, and meansfor flowing a deodorization gas in a countercurrent direction from saidoil in said column, said distillation column (3) being filled withstructured packing material, a plurality of trays for the collection andtreatment of said oil, each provided with at least one drainage outletin its lower part, said plurality of trays providing locations forbatchwise treatment of said oil with said deodorization gas, an inlet(7) for said oil, a connection (2) to a vacuum source in an upper partof said vessel (1), and an outlet (9) for said oil in a lower part ofsaid vessel (1).
 2. The deodorization plant according to claim 1,wherein the column (3) is arranged above the trays in the vessel.
 3. Thedeodorization plant according to claim 1, wherein the trays are providedwith means (12, 12') for addition of said deodorization gas to the oilnear to the respective bottoms of the trays.
 4. The deodorization plantaccording to claim 1, further comprising means (13) for supplyingdeodorization gas in the tray in the lower part of the vessel nearest tothe outlet from the same.
 5. The deodorization plant according to claim1, wherein the vessel is provided with tubes (10, 11) which connectspaces above each tray with a space provided under the column.
 6. Thedeodorization plant according to claim 1, further comprising a heatexchanger (14) which is divided into a plurality of sections and isconnected to the outlet (9) from the vessel, said sections beingconnected to each other by cut-off valves (19, 19') and provided withmeans for supplying deodorization gas.